Transcript video slide - CARNES AP BIO

Chapter 45
Hormones and the Endocrine
System
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
YOU MUST KNOW
• Two ways hormones affect target organs.
• The secretion, target, action, and regulation of
at least three hormones.
• An illustration of both positive and negative
feedback in the regulation of homeostasis by
hormones.
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The Body’s Long-Distance Regulators
• The endocrine system and the nervous system
act individually and together in regulating an
animal’s physiology.
– The endocrine system of an animal is the sum of all its
hormone-secreting cells and tissues.
– Endocrine glands are ductless and secrete hormones
directly into body fluids.
– Hormones are chemical signals that cause a response
in target cells.
– Positive and negative feedback regulates most
endocrine secretion.
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Control Pathways and Feedback Loops
Pathway
Example
Low blood
glucose
Stimulus
Receptor
protein
Pancreas
secretes
glucagon ( )
Endocrine
cell
Blood
vessel
Target
effectors
Response
Pathway
Stimulus
Example
Example
Pathway
Suckling
Hypothalamic
neurohormone
released in
response to
Sensory
neural and
neuron
hormonal
signals
Hypothalamus
Sensory
neuron
Hypothalamus/
posterior pituitary
Neurosecretory
cell
Posterior pituitary
secretes oxytocin
Blood ( )
vessel
Stimulus
Neurosecretory
cell
Hypothalamus
secretes prolactinBlood
releasing
vessel
hormone ( )
Liver
Glycogen
breakdown,
glucose release
into blood
(a) Simple endocrine pathway
Target
effectors
Response
Smooth muscle
in breast
Milk release
Anterior
pituitary
secretes
Endocrine prolactin ( )
cell
Blood
vessel
(b) Simple neurohormone pathway
Target
effectors
Response
Figure 45.2a–c
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Mammary glands
Milk production
(c) Simple neuroendocrine pathway
Mechanisms of Hormone Action
• Hormones and other chemical signals bind to target
cell receptors, initiating pathways that culminate in
specific cell responses. There are basically two
mechanisms of hormone action:
–
Cell Surface Receptors: bind the hormone, and a signal
transduction pathway is triggered, eliciting a response to the
signal.
• Ex: The binding of epinephrine to liver cells causes a cascade
that leads to the conversion of glycogen to glucose.
–
Intracellular Receptors: bound by hormones that are lipidsoluble. The receptor then acts as a transcription factor, causing
a change in gene expression.
• Ex: Testosterone and estrogen enter the nuclei of target cells,
bind the DNA, and stimulate transcription of certain genes.
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Varying Degrees of Hormonal Effect
• The hormone epinephrine has multiple effects
in mediating the body’s response to short-term
stress
Different receptors
different cell responses
Epinephrine
Epinephrine
Epinephrine
a receptor
b receptor
b receptor
Glycogen
deposits
Vessel
dilates
Vessel
constricts
(a) Intestinal blood
vessel
Figure 45.4a–c
(b) Skeletal muscle
blood vessel
Different intracellular proteins
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Glycogen
breaks down
and glucose
is released
from cell
(c) Liver cell
different cell responses
Paracrine Signaling by Local Regulators
• In a process called paracrine signaling
– Various types of chemical signals elicit
responses in nearby target cells
• Paracrine signaling involves local regulators –
they convey messages between neighboring
cells (as opposed to long-distance endocrine
signaling by hormones).
– These can elicit cell responses more quickly
than hormones.
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The Major Human Endocrine Glands
Hypothalamus
Pineal gland
Pituitary gland
Thyroid gland
Parathyroid glands
Hypothalamus
Neurosecretory
cells of the
hypothalamus
Axon
Adrenal glands
Pancreas
Posterior
pituitary
HORMONE
TARGET
Anterior
pituitary
ADH
Kidney tubules
Ovary
(female)
Oxytocin
Mammary glands,
uterine muscles
Testis
(male)
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Relation Between the Hypothalamus and Pituitary Gland
•
Other hypothalamic cells produce tropic hormones that are secreted
into the blood and transported to the anterior pituitary or
adenohypophysis
Tropic Effects Only
FSH, follicle-stimulating hormone
LH, luteinizing hormone
TSH, thyroid-stimulating hormone
ACTH, adrenocorticotropic hormone
Neurosecretory cells
of the hypothalamus
Nontropic Effects Only
Prolactin
MSH, melanocyte-stimulating hormone
Endorphin
Portal vessels
Nontropic and Tropic Effects
Growth hormone
Hypothalamic
releasing
hormones
(red dots)
HORMONE
TARGET
Figure 45.8
FSH and LH
Testes or
ovaries
TSH
Thyroid
Endocrine cells of the
anterior pituitary
Pituitary hormones
(blue dots)
ACTH
Prolactin
MSH
Endorphin
Adrenal
cortex
Mammary
glands
Melanocytes
Pain receptors
in the brain
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Growth hormone
Liver
Bones
Human Endocrine Glands & Their Hormones
Table 45.1
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Human Endocrine Glands & Their Hormones
Table 45.1
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Nonpituitary Hormones
• Nonpituitary hormones help regulate metabolism,
homeostasis, development, and behavior
• Many nonpituitary hormones regulate various
functions in the body and include:
– Thyroid hormones
– Parathyroid Hormone and Calcitonin
– Insulin and Glucagon
– Adrenal Hormones
– Glucocorticoids, such as cortisol
– Mineralocorticoids, such as aldosterone
– Sex hormones
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Thyroid Hormones
• The thyroid gland consists of two lobes located on
the ventral surface of the trachea
– Produces two iodine-containing hormones,
triiodothyronine (T3) and thyroxine (T4)
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Negative Feedback Loops Control Thyroid Hormones
• The hypothalamus and anterior pituitary control
the secretion of thyroid hormones through two
negative feedback loops
Hypothalamus
Anterior
pituitary
TSH
Thyroid
Figure 45.9
T3 +
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T4
Hyperthyroidism
• The thyroid hormones play crucial roles in
stimulating metabolism and influencing
development and maturation
Figure 45.10
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Parathyroid Hormone and Calcitonin:
• The maintainence of blood calcium level is one example of
how homeostasis is maintained by negative feedback.
Thyroid gland
releases
calcitonin.
Calcitonin
Reduces
Ca2+ uptake
in kidneys
Stimulates
Ca2+ deposition
in bones
Blood Ca2+
level declines
to set point
STIMULUS:
Rising blood
Ca2+ level
Homeostasis:
Blood Ca2+ level
(about 10 mg/100 mL)
STIMULUS:
Falling blood
Ca2+ level
Blood Ca2+
level rises
to set point
Stimulates
Ca2+ release
from bones
Parathyroid
gland
PTH
Increases
Ca2+ uptake
in intestines
Figure 45.11
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Active
vitamin D
Stimulates Ca2+
uptake in kidneys
Maintenance of Glucose Homeostasis
Body cells
take up more
glucose.
Insulin
Beta cells of
pancreas are stimulated
to release insulin
into the blood.
Liver takes
up glucose
and stores it
as glycogen.
STIMULUS:
Rising blood glucose
level (for instance, after
eating a carbohydraterich meal)
Blood glucose level
declines to set point;
stimulus for insulin
release diminishes.
Homeostasis:
Blood glucose level
(about 90 mg/100 mL)
Blood glucose level
rises to set point;
stimulus for glucagon
release diminishes.
Figure 45.12
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Liver breaks
down glycogen
and releases
glucose into
blood.
STIMULUS:
Dropping blood glucose
level (for instance, after
skipping a meal)
Alpha cells of pancreas
are stimulated to release
glucagon into the blood.
Glucagon
Diabetes Mellitus
• Diabetes mellitus, perhaps the best-known endocrine
disorder
– Is caused by a deficiency of insulin or a decreased
response to insulin in target tissues
– Is marked by elevated blood glucose levels
• Type I diabetes mellitus (insulin-dependent diabetes)
– Is an autoimmune disorder in which the immune
system destroys the beta cells of the pancreas
• Type II diabetes mellitus (non-insulin-dependent diabetes)
– Is characterized either by a deficiency of insulin or,
more commonly, by reduced responsiveness of target
cells due to some change in insulin receptors
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Adrenal Hormones: Response to Stress
• The adrenal glands are adjacent to the kidneys
and are actually made up of two glands: the
adrenal medulla and the adrenal cortex
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Stress Hormones from the Adrenal Cortex
• Hormones from the adrenal cortex also
function in the body’s response to stress and
fall into three classes of steroid hormones:
• Glucocorticoids, such as cortisol
– Influence glucose metabolism and the immune
system
• Mineralocorticoids, such as aldosterone
– Affect salt and water balance
• Sex hormones
– Are produced in small amounts
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Stress and the Adrenal Gland
Stress
Spinal cord
(cross section)
Nerve
signals
Hypothalamus
Releasing
hormone
Nerve
cell
Anterior pituitary
Blood vessel
Adrenal medulla
secretes epinephrine
and norepinephrine.
Nerve cell
Adrenal cortex
secretes
mineralocorticoids
and glucocorticoids.
ACTH
Adrenal
gland
Kidney
(a) Short-term stress response
Effects of epinephrine and norepinephrine:
1. Glycogen broken down to glucose; increased
blood glucose
2. Increased blood pressure
3. Increased breathing rate
4. Increased metabolic rate
Figure 45.13a,b
5. Change in blood flow patterns, leading to
increased alertness and decreased digestive
and kidney activity
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(b) Long-term stress response
Effects of
mineralocorticoids:
1. Retention of sodium
ions and water by
kidneys
2. Increased blood
volume and blood
pressure
Effects of
glucocorticoids:
1. Proteins and fats
broken down and
converted to glucose,
leading to increased
blood glucose
2. Immune system may
be suppressed
Gonadal Sex Hormones
• The gonads (testes and ovaries) produce most
of the body’s sex hormones: androgens,
estrogens, and progestins
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Melatonin and Biorhythms
• The pineal gland, located within the brain
secretes melatonin
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Invertebrate Regulatory Systems
• In insects, molting and development are
controlled by three main hormones:
Brain
1 Neurosecretory cells in the brain produce
brain hormone (BH), which is stored in
the corpora cardiaca (singular, corpus
cardiacum) until release.
Neurosecretory cells
Brain
hormone (BH)
Corpus cardiacum
Corpus allatum
Low
JH
Prothoracic
gland
Ecdysone
Juvenile
hormone
(JH)
2 BH signals its main target
organ, the prothoracic
gland, to produce the
hormone ecdysone.
3 Ecdysone secretion
from the prothoracic
gland is episodic, with
each release stimulating
a molt.
EARLY
LARVA
Figure 45.15
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LATER
LARVA
PUPA
4 Juvenile hormone (JH), secreted by the corpora allata,
determines the result of the molt. At relatively high concentrations of JH, ecdysone-stimulated molting produces
another larval stage. JH suppresses metamorphosis.
But when levels of JH fall below a certain concentration, a
pupa forms at the next ecdysone-induced molt. The adult
insect emerges from the pupa.
ADULT